Tue April 13, 2021 4:00 pm

CUA Virtual Seminar – Probing graphene’s orbital magnetism with NV centers in diamond


Many exotic phenomena in condensed matter physics, including quantum hall effects, topological states of matter, and magnetoelectric effects, can be understood in terms of the Berry phase of electrons in a solid. One of the first observations of such an effect was in graphene, whose Berry phase of pi shifts a Landau level at zero energy, resulting in an unconventional quantum hall effect and a diverging magnetic susceptibility at the Dirac point. We introduce a novel technique for measuring the susceptibility of 2D materials using nitrogen vacancy centers implanted in a diamond substrate. We use these wireless susceptometers to non-invasively measure the gate dependent magnetic response of graphene and find the predicted sharp increase in signal near the Dirac point. The local nature of our measurements permit us to map this signal at different locations under the device. This technique gives insight into the origins of the quantum hall effect in graphene, and more importantly provides a straightforward method for measuring orbital magnetism and other Berry phase effects in many 2D materials such as topological insulators and twisted structures that exhibit emergent moire potentials.

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